The Acanthostega is the oldest known tetrapod. Is Ichthyostega predecessor and successor of Tiktaalik. It is of the first vertebrates that poked their heads out of the water to see what had out and hunt insects and arthropods near water. Remember that a tetrapod is one animal that has four legs, and who uses them.

It is the oldest known tetrapod. It was the first animal that had the bone structure needed to walk out of the water. A structure, perfected, was the basis for all other tetrapods (amphibians, reptiles, mammals and birds).

How was this prehistoric animal?

Similar to Ichthyostega, no more than a meter in length and its legs were 8 fingers. And like Tiktaalik, the Acanthostega had a disembodied skull that could move while the body ... Unlike fish.

Like early amphibians, the first ones out of the water, his breathing was a simple combination of lungs and gills.

This evolution firstborn old, lived in the shallow waters of the Devonian, 370-360 million years ago.

Tiktaalik was primarily the characteristics of a fish, but with the tips forming skeletal structures similar to an arm, similar to those of crocodiles, including shoulder, elbow and wrist. He had the sharp teeth of a predator, and his neck could move independently of his body, it is not possible in other fish. The animal also had a flat skull like the crocodile eyes on the top of the head, suggesting that spend much time looking up, neck and ribs like those of tetrapods, which will serve to support the body and help to breathe through lungs, a long snout can catch prey on land, and a gill opening, in higher animals, would subsequently become heard. Its discoverers felt that, in all likelihood, Tiktaalik flexed its proto-limbs in the main river bed and could have pushed himself to the shore for brief periods. These specimens reached a size of 1.2 to 2.75 meters.

He lived in the Devonian period about 375 million years.

Excellently preserved remains of Tiktaalik in 2004 were found on Ellesmere Island in Canada.

Along with Ichthyostega, Coelacanth and Acanthostega is one of the prehistoric animals that show as was the transition from fish to tetrapod.